The present invention relates generally to a hydropneumatic damping device and more particularly to a hydro-pneumatic damping device, which is particularly adapted for use with a spring leg of a vehicle. The invention is particularly concerned with the type of hydro-pneumatic damping devices comprising:
an inner cylinder having an axis and two ends, PA1 a central cavity defined within said inner cylinder between said two ends, PA1 an outer container surrounding said inner cylinder, said outer container having two ends adjacent respective ends of said inner cylinder, PA1 an annular cavity defined between said inner cylinder and said outer container, PA1 first and second closure means closing said two ends of said cylinder and said container, PA1 piston rod passage means through the first ones of said closure means, PA1 fluid passage means between said central cavity and said annular cavity adjacent the second ones of said closure means, PA1 first fluid throtteling means associated to said fluid passage means, PA1 a piston rod axially extending through said piston rod passage means and into said central cavity, PA1 a piston unit mounted on said piston rod within said central cavity and defining two working chambers within said cavity, a first working chamber adjacent said first closure means and a second working chamber adjacent said second closure means, PA1 fluid connecting means connecting said two working chambers across said piston unit, PA1 second fluid throtteling means associated to said fluid connecting means, PA1 a body of liquid at least within the central one of said cavities, PA1 a body of gas within said annular cavity. PA1 a sealing unit engaging said piston rod and having an inner end adjacent said outer end of said cylinder closing unit and PA1 venting passage means between said first working chamber and said annular cavity extending across said cylinder closing unit and inside said inner end of said sealing unit.
Such a hydro-pneumatic damping device is known from German Pat. No. 11 46 705.
With such hydro-pneumatic damping device it is important, that the first working chamber which is regularly the upper working chamber, is always filled with liquid. The presence of gas in this first working chamber is objectionable because the function of the device is altered by such presence of gas. It could happen due to the presence of gas in the first working chamber, that this gas is compressed, when the piston rod moves outward from the central cavity and that no damping effect is achieved. Therefore it is of high importance, that a gas which has been collected in the upper or first working chamber is brought into the annular cavity.
From the above mentioned German Pat. No. 11 46 705 it is known, that the first closure means comprise a cylinder closing unit surrounding said piston rod and having an inner end adjacent said first working chamber and an outer end,
With the known device it is still possible, that during the inward movement of the piston rod, when the pressure within the first working chamber is decreased and the pressure within the annular cavity is increased air is pumped from the annular cavity into the first working chamber, so that the function of the hydro-pneumatic damping device is affected.
A further disadvantage of the known device is, that it can be mounted only in such a position, that the piston rod is substantially vertically directed upwards. At a small inclination already the function of the known hydo-pneumatic device is affected.
The present invention is directed towards avoiding the disadvantages of the known construction and toward the provision of a hydro-pneumatic damping device in which substantially no air can enter from the annular cavity into the first working chamber, even when the device of this invention is mounted in an inclined position.